Broken SMM procedures in XPS 9570 firmware

Hello. I'm helping to add support for the Dell XPS 9570 in the Linux module "dell-smm-hwmon", that is used to read temperatures and fan speed by means of SMM calls.

I've noticed that the following procedures are broken:

- 0x11a3: should return a numeric value that represents the type of the sensor based on the index provided as first argument
- 0x03a3: should return a numeric value that represents the type of the fan based on the index provided as the first argument

These two procedures always return 0xffff, even for valid indexes (valid because they can identify sensors and fan correctly when used in other procedures, for example the one to read the actual temperature of a sensor or the one to read the speed of a fan).

When the same procedures (0x11a3 and 0x03a3) are run on XPS 9560 they return proper values instead.

More information can be found here: https://www.spinics.net/lists/linux-hwmon/msg04732.html

I'm running firmware version 1.6.0